(1) Field of the Invention
The invention relates to a method of quickly determining a dimension of a circular object using sensors to measure time instants without the need of a ruler for measuring a diameter of the circular object.
(2) Description of the Prior Art
In the prior art for measuring a diameter of a coin, two sensors are disposed on a track on which the coin rolls in one method. The diameter of the coin is calculated according to time instants when the coin reaches and leaves the sensors, as shown in FIG. 4.
However, this dual-sensor design needs the longer stable track so that four time instants for the calculation of the diameter may be obtained. Referring to FIG. 4, if an equivalent chord length drawn by a circular object on the sensor is equal to C, and a gap between the sensors is equal to U, then the required minimum length of the stable track has to be equal to (C+U).
However, some coin inspection mechanisms have predetermined dimension limitations. For example, a top entry (falling type) coin inspection mechanism has the standard specification with the fixed smaller dimension. Because the dual-sensor design needs the longer stable track length, it is usually difficult to place the dual-sensor design into the coin inspection mechanism with the limited dimension.